1. Field of the Invention
This invention relates generally to copier apparatus, and more particularly to a fuser assembly mechanism for driving a backup roll either towards or away from a hot roll.
2. DESCRIPTION OF THE PRIOR ART
Hot roll fuser design requires the loading and unloading of the backup roll and hot roll to accomplish fusing, to minimize backup roll temperatures, to reduce power consumption and to enhance copy handling reliability. The hot roll is usually a stationary member whereas the backup roll is moved into and out of contact with the hot roll. Since the hot roll is typically nongrounded electrically for temperature sensing and control, and to insure mechanical integrity of drive components, the backup roll is mechanically powered (rotationally) to process a copy at the fuser station. The rotated backup also serves as a power takeoff for the drive of other essential copy handling enhancement mechanism, i.e., pinch roll and backup roll scraper system. All of these requirements place severe limitations on the fuser roll closure mechanism while at the same time not degrading copy handling reliability. The typical prior art roll closure mechanism includes a lever system of low mechanical advantage. With this type of mechanism, the moving backup roll requires the use of anti-backlash gearing, chains with idlers and other associated mechanical hardware in order to minimize the effects of changing center distances between drive components. Backlash and high compliant drive components significantly reduce copy handling reliability and fuse grade through variations in time spent at the fusing nip.